The influence of atrial size and elasticity on the left atrial pressure tracing

Intraoperative Doppler color flow mapping for decision-making in valve repair for mitral regurgitation. Technique and results in 100 patients

Mitral valve repair provides substantial advantages over mitral valve replacement in patients with severe mitral regurgitation. However, because of the possibility of persistent regurgitation, an intraoperative technique is needed to provide an immediate and accurate assessment of the adequacy of the repair before closure of the chest. One hundred patients with pure mitral regurgitation were studied with intraoperative epicardial Doppler color flow mapping immediately before and after valve repair. Intraoperative assessment of the severity of mitral regurgitation showed good agreement with preoperative left ventriculography and with standard precordial Doppler echocardiography before and after surgery. Postrepair intraoperative Doppler studies showed satisfactory surgical results in 92 patients. Postrepair intraoperative Doppler studies in the remaining eight patients demonstrated unsatisfactory results: persistent significant regurgitation in four, systolic anterior motion of the mitral valve with dynamic left ventricular outflow tract obstruction in three, and a persistent flail leaflet in one. In six of the eight patients, further surgery was performed during the same thoracotomy. In two patients, the intraoperative postrepair Doppler findings of persistent regurgitation were confirmed on precordial Doppler studies within 5 days, and mitral reoperation was required. Intraoperative epicardial Doppler color flow mapping provided a "safety net" that ensured a successful outcome in all 100 patients by providing the surgeon with a direct means to assess the success of the operation and the need for further surgery.

Role of the left atrium in adaptation of the heart to chronic mitral regurgitation in conscious dogs

The manner in which the left atrium adapts to chronic mitral regurgitation and the role of the adapted left atrium as a modulator of excessive central blood volume were analyzed in seven conscious dogs, instrumented with high-fidelity pressure transducers and ultrasonic dimension gauges for measurement of left atrial and left ventricular pressure and cavity size. After obtaining data in a control situation, mitral regurgitation was produced by transventricular chordal sectioning. Heart rate was matched by right atrial pacing. In the "early" stage (7-14 days), left ventricular end-diastolic and mean left atrial pressures increased from 6 to 16 mm Hg and from 4 to 12 mm Hg, respectively. Both left ventricular end-diastolic segment length and left atrial diameter prior to atrial contraction increased by 7%. In the "late" stage (20-35 days), despite significant decreases in left ventricular filling pressure (11 mm Hg) and left atrial pressure (8 mm Hg), there was a continuous increase in left ventricular end-diastolic dimension (10%) and atrial end-diastolic diameter (10%). After the onset of mitral regurgitation, the left atrium performed greater work with a more enlarged cavity. Left atrial chamber stiffness was progressively decreased. These changes were associated with progressive increase in the left atrial diameter at zero stress, and there was a significant increase in the diameter of the left atrial myocyte. These results indicate that during chronic mitral regurgitation, the left atrium enlarges in size and mass, with a more potent booster action. The left atrial chamber becomes more compliant. Thus, the enlarged left atrium appears to exert an important compensatory mechanism in the case of excessive central blood volume by buffering pressure rise in the atrium and by providing an adequate ventricular filling volume.

Limitations of pulmonary wedge V waves in diagnosing mitral regurgitation

To study the usefulness of large V waves in pulmonary capillary wedge tracings in establishing the diagnosis of mitral regurgitation, data on 1,021 consecutive cardiac catheterizations were reviewed. Wedge tracings were obtained by Swan-Ganz catheterization in 208 patients, usually because of suspected valve disease. One hundred two patients had no trace of mitral regurgitation angiographically, 69 had mild to moderate and 37 had severe regurgitation. V waves were graded as trivial (less than 5), intermediate (5 to 10) or large (10 or more mm Hg above mean wedge pressure). Of 50 patients with large V waves, 18 (36 percent) had no or trace mitral regurgitation; these included 5 with mitral stenosis, 3 with a mitral valve prosthesis, 4 with coronary disease and congestive failure, 2 with aortic valve disease and congestive failure and 2 with a ventricular septal defect. Of 37 patients with severe mitral regurgitation, 16 (43 percent) had large and 12 (32 percent) had trivial V waves. Thus, mitral regurgitation is the most common cause of large V waves; however, large V waves are neither highly sensitive nor specific for severe regurgitation. Increased left atrial compliance may be associated with trivial V waves in the presence of severe regurgitation. Mitral obstruction, congestive heart failure and ventricular septal defect may all be associated with large V waves in the absence of significant mitral regurgitation.

The value of left parasternal impulse recordings in the assessment of mitral regurgitation

Left parasternal cardiograms were recorded at the fifth intercostal space in 30 patients with mitral regurgitation. Early systolic outward movements (E), late systolic outward movements (LOM), and the ratio of the LOM area to the total area occupied by the left parasternal cardiogram (LPC area) were examined. Thirteen patients had pure mitral regurgitation due to ruptured chordae tendineae (ten patients) or "floppy mitral valve" (three patients). In these patients LOM/E correlated significantly with the regurgitation volume determined by the difference between angiographic and Fick stroke volumes, ( r = 0.93, P < 0.01), and with the height of the "v" wave in the pulmonary artery wedge pressure tracings ( r = 0.79; P < 0.01). Simultaneous recordings of left parasternal movements and pulmonary wedge pressures in eight patients in this group showed a close relationship between LOM and "v" waves.

Fourteen patients had rheumatic heart disease and mitral regurgitation associated with mitral stenosis of varying degrees of severity. In this group there was no significant correlation between LOM/E or LOM area/LPC area and the regurgitation volume or the height of the "v" wave. Of three patients who had congenital atrial septal defect in addition to mitral regurgitation, none had prominent LOM in the left parasternal cardiogram.

This study suggests that if mitral stenosis and atrial septal defect can be excluded on clinical evidence, the left parasternal cardiogram may be used to obtain a noninvasive assessment of the severity of mitral regurgitation, particularly in patients with recent onset of the disease.

The second sound-mitral opening snap (A2-OS) interval during exercise in the evaluation of mitral stenosis

Cardiac catheterization and phonocardiography data were obtained from patients with mitral stenosis at rest and during exercise. There was a linear relationship between the percentage decrease of the interval from closure of the aortic valve to the mitral valve opening snap (A2-OS) and the percentage increase [see figure in the PDF file] of the left atrial mean pressure from rest to exercise. The duration of the A2-OS interval was an effective indicator of the level of the left atrial mean pressure during exercise. The duration of the A2-OS interval during exercise allowed separation of patients with mild stenosis from those with moderate or severe stenosis but could not be used to distinguish moderate stenosis from severe stenosis.

Determination of Pulmonary Blood Volume by Single Intravenous Injection of One Indicator in Patients with Normal and High Pulmonary Vascular Pressures

Determinations of the pulmonary blood volume were carried out in 12 patients with pulmonary hypertension and in 12 patients with normal pressures in the pulmonary circulation, by the use of a single intravenous injection of one indicator, blood sampling being made through catheters in the pulmonary artery and left atrium and connected with two densitometers of similar characteristics. Pulmonary blood volume measured by this technic includes the major portion of, or the entire left atrial volume. Values obtained from duplicate or triplicate determinations performed in each patient have shown that this technic provides very good reproducibility of the results expressed by an average percentile variation around the mean equal to 3.2±2.7. The mean pulmonary blood volume as referred to body surface area was 375±97 ml./M. 2 for patients with pulmonary hypertension, and 310±21 ml./M. 2 for patients with normal pulmonary intravascular pressures. This difference was found to be significant ( p <0.05) but was attributed, at least in part, to a difference in the mean left atrial volume between the two groups studied.

Some possible advantages and limitations of the method, as well as the poor correlation between pulmonary blood volume and other variables, like pulmonary intravascular pressures, stroke volume, and cardiac output, were discussed.

The Syndrome of Severe Mitral Regurgitation with Normal Left Atrial Pressure

It has been generally thought that significant elevations of the left atrial and pulmonary vascular pressures occur in patients with mitral regurgitation of sufficient severity to produce serious disability and gross enlargement of the left atrium. Ten patients with severe mitral regurgitation have been encountered in whom gross left atrial enlargement was accompanied by normal left atrial and pulmonary artery pressures. These patients ranged in age from 8 to 49 years, all were in functional classes III or IV, and the average duration of symptoms was 7.3 years. Nine patients had rheumatic mitral regurgitation while one had a congenital lesion. Atrial fibrillation and the physical findings of pure mitral regurgitation were present in all patients, as was striking left atrial enlargement on their roentgenograms. Left atrial pressure, determined by left heart catheterization, averaged 9.1 mm. Hg and did not exceed 12 mm. Hg in any patient, and the V wave was not particularly prominent. The cardiac index was markedly depressed and averaged 2.0 L./min./M. 2 B.S.A.

The observed discrepancy between left atrial size and pressure must reflect a disturbance in the compliance of the left atrial wall. It is suggested that long-standing mitral regurgitation may modify the mechanical characteristics of the atrial wall and that the presence of a normal left atrial pressure must not be assumed to exclude the presence of severe mitral regurgitation. The manner in which variations in left atrial compliance affect the clinical picture of mitral regurgitation and the selection of patients for operative intervention are discussed.